Scientists Discover Singing Mice

By Walter Butler

For decades, scientists have been aware of the high-frequency sounds that male mice produce whenever they pick up the scent of a female mouse. The babbling sounds are undetectable by human ears, but to a female mouse the noises probably sound like the crooning of Mouse Torme. Scientists have always assumed the chatterings had something to do with courtship, but they have not been certain.

They are now certain, however, that the sounds aren’t so much babbling nonsense but more complex and interesting than previously thought. "It soon became ... apparent that these vocalizations were not random twitterings but songs," said researcher Timothy Holy. "There was a pattern to them. They sounded a lot like bird songs." The high-frequency sounds, undetectable by human ears, were recorded by Washington University School of Medicine researchers and amplified for human ears. If the analysis of the sounds is confirmed, that male mice emit them to attract female mice, then mice can be added to the list of creatures that are known to sing to capture the attention of the opposite sex. That short list includes not only songbirds, but also porpoises, humpback whales, a variety of insects, and possibly bats.

Holy and his colleague Zhongsheng Guo were studying the brain response in male mice to chemical signals emitted by female mice when they discovered that the sounds the male mice were making were more like songs than squeaks. They recorded the sounds with a microphone, then reconstructed them four octaves lower so they could study them. When they did, the sounds met two criteria that define a song—distinct syllables and recurring themes. "There was joy in this discovery," Holy said. "We didn't expect it." He said the finding was not just random perception, but a "very careful quantitative analysis of sounds."

Animal communication expert Peter Marler, a behavioral neurobiologist at the University of California, believes that if male mice are producing songs, then scientists should research how those sounds develop and whether mice—like birds—are able to learn new sounds. According to Marler, scientists know "extraordinarily little" about how the human brain helps people learn how to speak. "We don't know even where to look in the (human) brain," he said. "If it were to turn out that (mice) songs are learned, and that parts of the brain are involved in learning, that might open a new area of investigation." Marler said that the only mammals known to learn new sounds are porpoises and whales, but "they’re not exactly ideal for study."

The remarkable discovery of mice singing to each other opens up the possibility of scientists using mice to study and develop treatments for autism and other communication disorders.